The mucous membrane is loosely attached to the muscular coat by the submucosa. Except during deglutition it lies in longitudinal folds which obliterate the lumen. Opening from the mucosa are lenticular glands, which may be seen on inflating an esophagus and looking through its transparent walls. The muscular coat of the esophagus is divided into two layers, an outer longitudinal and an inner circular layer. The outer fibrous sheath connects the esophagus loosely to the surrounding structures. _Function._—The function of the esophagus is to give passage way for the food from the pharynx to the crop and from the crop to the proventriculus. =The Crop= (Fig. 35, No. 2; Figs. 30 and 31). _Location and Shape._—The crop, or ingluvies, saccular in shape, is located at the entrance of the thorax and just to the right of the median line. The first portion of the esophagus empties into the crop superiorly and inferiorly the crop opens into the second portion of the esophagus. Like the esophagus the crop is capable of great distension. _Structure._—The wall of the crop is composed of four coats, the mucous membrane, submucosa, muscular and the outer fibrous. The crop is lined with mucous membrane containing mucous glands which secrete a mucus to keep the surface moist. The surface of the mucous membrane is covered by stratified squamous epithelium. The submucosa connects the mucous membrane to the muscular coat. The wall of the crop is provided with strong muscles. The fibrous coat, or tunic, connects it with the surrounding structures. _Function._—The crop is a storehouse for the food during the hours of feeding, the food when needed by the stomach being gradually discharged from the crop by the contraction of its muscular walls. The subcutaneous cervical muscles which cover this reservoir aid in this discharge. In the _act of deglutition_, the food, after being subjected to the fluid supplied in the mouth by the adjacent glands, is poised upon the tongue and swallowed partly by a sudden jerk of the head, and partly by means of the pressure of the tongue against the hard palate, the food then passes down the esophagus and lodges first in the crop, till needed by the stomach, when it is passed through the second portion of the esophagus to the first portion of the stomach, the proventriculus. The time during which food remains in the crop depends upon the nature of the food. Animal food will, in part, be retained about eight hours and vegetable foods may not all be passed on for from sixteen to eighteen hours. =The Stomach= (Fig. 31, No. 7; Fig. 32, _B_).—The stomach, or ventriculus, of fowls is made up of two portions, namely, the pars glandularis, or proventriculus, and the pars muscularis, or gizzard.